1. Field of the Invention
The present invention relates to a cleaning apparatus, and in particular to a high reach anti-static cleaning apparatus.
2. Description of the Related Art
Vacuum cleaning apparatus are known and used in a variety of situations for lifting debris such as dust, dirt, or other loose contaminants, from a surface. Generally, such vacuum cleaning apparatus include a main suction unit housing an electric motor driven fan and a dust container, and a flexible hose. In use, the electric fan establishes a strong flow of air through the flexible hose, and into the main body, where an air filter element separates dust and debris entrained in the incoming flow of air, causing the separated dust and debris to be deposited in the dust container whilst exhausting the filtered air from the suction unit to the atmosphere. In this way, dust and debris may be lifted from a surface by the flow of air into an open end of the hose, carried by entrainment in the flow of air along the hose to the suction unit, and collected in the dust container for convenient disposal later.
A problem with such conventional vacuum cleaning systems is that of electrostatic discharge from the hose to objects in the surrounding environment. As is well known, the flow of air and entrained dust particles through the hose and associated attachments of the cleaner causes triboelectric charging of the hose and its attachments. This results in a build up of static electric charge in the electrically insulative or electrically isolated conductive components of the hose and attachments. If the hose is then brought sufficiently close to a conductive body, such as a grounded conductive workpiece or earthed metal pipework, an electrostatic discharge may occur.
Such electrostatic discharges are undesirable. They can be damaging to sensitive electronic components, for example, computing equipment, and can result in an unpleasant electric shock to a user of the equipment. Further, a particular problem exists in commercial and industrial situations, in the presence of flammable products, or where gases and airborne particulates create an explosive atmosphere. In such environments, a spark caused by an electrostatic discharge may cause ignition of the atmosphere and result in an explosion. Accordingly, in many jurisdictions, regulations are in place requiring certification of electrical equipment, such as vacuum cleaning apparatus, for use in explosive atmospheres. In Europe, a set of directives and standards referred to as ATEX define the technical requirements to which equipment used in explosive atmospheres must comply, the most recent of which regulations are implemented in the United Kingdom by the Dangerous Substances and Explosive Atmospheres Regulations.
An approach to avoiding static charge build ups, and reducing the risk of electrostatic discharge from vacuum cleaning apparatus, is to connect earthing straps to the hose of the vacuum cleaner. In this way, charge generated in the hose by the passage of air therethrough, is dissipated to ground. However, such arrangements are less than ideal when considering portable equipment, for example, a portable suction cleaning unit, as the earthing straps must remain connected to electrical earth during operation, and so tend to hinder mobility of the apparatus.
A further problem exists however in that it is common for vacuum cleaning units to be equipped with a rigid extendable pole having interchangeable cleaning heads, which is attached to the end of the flexible hose. In this instance, even if the flexible hose were to be grounded using earthing straps, static charge will still accumulate in the other ungrounded components, for example, the cleaning heads, and so the risk of electrostatic discharge is not avoided.